"I'm riding western and in western you ride in a curb, I don't need it for control"
It sounds like you're gonna do what you do, but for others, here's the rationale: With a kid, the curb bit becomes something that gets caught on stuff, and it becomes something the kid occasionally yanks on and hurts the horse's mouth(I once actually found a kid climbing up one rein, with the poor sweet beginner horse standing stock still with her eyes bugging out, cut the snot out of the horse's mouth), or drops the rein, the horse steps on it....ow for the horse. Another time, the curb rein went under the stirrup, that was u-u-ugly.
Most western horses, unless their mouths have been hardeneded through bad training, will go back in a snaffle for a ride with a kid and be just fine. Then one has one less thing to go wrong.
Safety in teaching kids is about making things a habit, and just whittling away at the list of 'what can go wrong'.